100 Things You Should Know about People: #3 — You Can Only Remember 3 to 4 Things At A Time (The Magic Number 3 or 4)

7 + – 2???

3 or 4???

Those of you who have been in the field of usability or user experience for a few years have probably heard the phrase “The Magic Number 7 Plus Or Minus 2”. This refers, actually, to what I would call an urban legend. Here’s the legend part:

Legend: “A guy named Miller did research and wrote a research paper showing that people can remember from 5 to 9 (7 plus or minus 2) things, and that people can process 7 plus or minus 2 pieces of information at a time. So you should only put 5 to 9 items on a menu, or have 5 to 9 tabs on a screen”.

Have you heard this? If you’ve been reading about usability for a while I’m sure you have. Well, it’s not quite accurate. Another guy named Baddeley questioned all this urban legend. Baddeley dug up Miller’s paper and discovered that it wasn’t a research paper, it was a talk that Miller gave at a professional meeting. And it was basically Miller thinking out loud about whether there is some kind of inherent limit to the amount of information that people can process at a time.

Baddeley conducted a long series of studies on human memory and information processing. And what he concluded is that the number is 3 to 4, not 5 to 9.

You can remember about 3-4 things (for about 20 seconds) and then they will disappear from memory unless you repeat them over and over. For example, let’s say you are driving in your car and talking on your cell phone (ok, you shouldn’t be doing that) and someone gives you a number to call. But you don’t have a pen handy, and anyway you are driving. So you try to memorize the number long enough to hang up from one call and dial the new number. What do you do? You repeat the number over and over (putting it back into short term memory each time, which buys you another 20 seconds). The interesting thing about phone numbers is that they are more than 3 or 4 numbers long. So they are hard to remember for more than 20 seconds.

712-569-4532

We also tend to chunk information into groups that have 3-4 items in them. So a phone number in the US is: 712-569-4532. Three chunks, with 3-4 items in each chunk. If you know the area code “by heart” (i.e., it’s stored in long term memory), then you don’t have to remember that, so one whole chunk went away. Phone numbers used to be easier to remember because you mainly called people in your area code, so you had the area code memorized (plus you didn’t even have to “dial” the area code at all). And then if you were calling people in your town each town had the same “exchange” — that is the 569 part of the phone number above. So all you had to remember was the last four numbers. No problem! I know I’m “dating” myself here by telling you how it used to be back in the old days. (I live in a small town in Wisconsin, and people here still give their number out as the last four digits only).

But that’s not all! Researchers working in the field of decision-making tell us that people can’t effectively choose between more than 3 to 4 items at a time.

So, what does all this mean? Can you really only have 4 items on a navigation bar? or 4 tabs on a screen, or 4 items on a product detail page at an e-commerce web site? No, not really. You can have more, as long as you group and chunk.

Here’s an example: At the Upton Tea site they have lots of tabs, but the tabs are not chunked into groups of 3 or 4.

So people will tend to do a partial scan and not even look at or read all the tabs. (I love their teas, by the way.. just wish they would do some work on the layout and emotional aspects of their site, but that’s probably another blog!).

I’ve covered more than 4 items in this blog post, so I’ll stop now! For those of you who like to read research here are some references:

One thing I’d like to add is, that the amount of time, that one is able to keep chunks within the working memory depends on the amount of chunks and the size of the chunks themselves. Both of these dimensions influence the time of rehearsal and thereby limit the time it can be kept from forgetting (Card, Moran, Newwell (1986)).

There is no need for people to remember the items they *see* on the screen, so whatever is the correct number, I find using it in this context questionable. I would rather apply those limits to mouse/touchscreen gestures, complicated keyboard shortcuts etc.

People do sometimes have to remember something from one screen to the next, so I think it’s still relevant to talk about remembering things on a screen. Besides remembering there is also the idea of just having to process more than 3-4 things or deciding amongst more than 3-4 things. The larger point I was trying to make is that 3-4 things is the magic number rather than 5-9 things.

But yes, I do agree that there are many other places that the 3-4 consideration should be applied.

In your book you say that more options means more attention but less convertions. I think category pages should list a last 6 options, extra work of pagination is not good for user. Large navigation schemas vs long category pages.

Just because people tend to only remember 3-4 items at a time in their short term memory should not be reason to group menu items in groups of 3-4. Because the menu items are always on the screen, there is not need to remember them, rendering the theory mostly useless. There may be other reasons that groupings of 3-4 could provide better usability, but it’s not because of memory, because we don’t need to remember it if it’s always in front of us to reference when needed.

I remember only having to dial 4 digits to call our neighbors. Grew up in Dewey, AZ. This also reminds me of going to the little general store. Picking out a candy bar was simple and quick since you only had one small isle of candy to choose from. Same with buying a soda, root beer, orange or pepsi.

Now I go into the candy isle(s) and it takes forever to decide, even for a creature of habit. The pre-frontal cortex is on overload at the local 7-11.

My friend’s father had a chain of hardware stores. He only had 3 variants of each item in his store. 3 types of TV’s, 3 radio’s, 3 stereo sets, 3 washing machines.
That made life easy for both his sales rep’s and for his customers.

The psychological tendancy is to choose the middle option of 3. So make the middle option slightly less expensive as the most expensive one. E.g. 1,25 euro; 2,25 euro and 2,50 euro. Thus you maximize your business.

Thank you for this evidence-based article, with references. Those of us who practice scientific social marketing will benefit from being able to review the research and consider your interpretation as well as alternatives. This moves us forward much more than opinions and critiques of your conclusions. Great work!

This is complete nonsense. It’s one thing to remember things, it’s a completely other to view and choose between things that you don’t need to remember. If you let UI design be controlled by the 3-to-4 rule you’ve obviously completely missed the point of how humans perceive things (perception is something else completely).

I went into shock when I read this post. How could I be so wrong for decades about the George Miller article?!? So I went back to the original. It was originally published in Psychological Review in 1956, not simply presented as a paper at a professional meeting. There is a difference between an opinion piece and a review article and a research report. A review article does not present new data as a research report does, but reports data from a number of research reports and provides an interpretation of the data from those reports. An opinion paper, on the other hand, outlines a theory which is then supported or disproved with data from future research. Miller’s paper reported data from approximately 18 experiments, the vast majority published in peer-reviewed journals. One of those published experiments was his own. So I really do think it is unfair to suggest that George Miller was just making things up.

Nor am I maligning Allan Baddeley’s work. While Miller is concerned with capacity (the point at which people make mistakes), it is not unreasonable to assume that people will start recoding or chunking information at a point below capacity, namely 3 – 4 items. From the standpoint of a communications professional, it is certainly safer to work with people’s chunking preferences rather than stretch things to the limits of their capacity. Therefore, I take no issue with your conclusions. But had you read the original article (which, as a classic, is reprinted in various places), you would not have described it as you did.